Re: jeep hubs, vacume woes
I am assuming that the xj vacuum disconnect is through a vacuum motor on the axle. This motor slides a splined sleeve over the two halves of the inner axle shaft, connecting the outer half of the inner shaft(follow?) of axle to the rotating inner half, making the open differential stop freespinning and forcing it to drive a front wheel.
Your front drive isn't working because you have a leak in the system. I would first inspect any hard plastic lines for cracks, and any steel lines for rust. One crack or pinhole will disable the system. I am guessing that you have just bought this truck? If so, do you suppose that the PO used the 4wd much? Disuse can allow those vacuum motors to corrode and freeze up. If your inspection turns up no bad lines, remove the motor and check the movement. it should move freely if all the lines are disconnected. You should be able to block off one or two of the hose connections to make the motor lock. If the diaphragm is intact, covering holes should trap air inside the motor, preventing you from sliding the shaft back and forth. If the shaft can still move, regardless of holes being covered, the diaphragm has been broken, and you need a new motor. Talk to your loan officer and your friendly local jeep dealer, and you should be back on the road in no time. Brendan
Proud owner of the world's best running Carter BBD